Heating system



Dec. 16, 1941. D. H. MCC RKLE 2,266,563

HEATING SYSTEM Filed Aug. 19, 1939 47 1 {l 45 U I M M. /.9 44 4 @A p.Zzaemor Patented Dec. 16, 1941 HEATING SYSTEM Donald H. McCorkle,Berkeley, Calif.

Application August 19, 1939, Serial No. 291,024

7 Claims.

This invention, a heating system, consists of a new and improved methodof establishing and maintaining a uniform room temperature devoid ofthermal stratification, and relates in particular to a new method ofthermostatically controlling the operation of warm-air furnaces,particularly those which are provided with forced draft heatdistributing and circulating means.

Warm air furnaces are now being quite genwhich opens and closes a fuelvalve for feeding the furnace, in accordance with the heat demands ofthe room in which the room thermostat is located. The fan or blowerintroducing the forced draft is thermostatically controlled by therelative heat within the furnace casing, and so arranged that when thetemperature within the casing has reached a predetermined value, the fanis automatically started and continues to operate until the temperaturewithin the casing drops below the starting value, at which timeoperation of the fan or blower is terminated.

With this type of forced draft control, the fan operates intermittentlywith full capacity cycles of short duration, resulting in a series ofon-andoil operating cycles, producing alternatelyoverheated andunderheated conditions of. the" rooms heated by the furnace. Inaddition, this method of operation results in such short periods ofcirculation that the warm and cold air in the rooms does not becomecompletely mixed, and thermal stratification ofthe warm and coldportions of the air immediately takes place each time the fan stops,resulting in cold floorsand the condition commonly termed cold seventy."

It is a well-recognized fact that in forceddraft warm air systems greatadvantage can be gained if the fan can be made to operate at increasedperiods of time. However, with register outlet velocities as generallycreated, air must be heated to approximately 100 F. to avoid discomfort,therefore under the conditions just described, extended operation of thefan is impractical and unsatisfactory.

There are several methods current for obtaining longer cycles of fanoperations, included in which is a two-stage thermostat designed tooperate a high-low burner; and an outdoor thermostat used in conjunctionwith the regular type of roomthermostat to modulate the burner capacity.Both systems lack in eificiency, precision and uniformity and thereforeincur serious objections, and do not attain the desired result.

With my system I propose to so control the furnace fire that the heatwill be delivered in accordance with requirements, and in such manherthat the fan will continue to operate for far greater periods of timefor each cycle, and to so control the heat within the furnace through.

interdependent, cooperative and selective control through existent room,duct, and furnace temperatures,' that the room temperature will bemaintained substantially uniform and free of thermal stratification.

The objects and advantages of this invention are as follows z, I

First; to provide a heating system which will maintain a substantiallyuniform room temperature, with the room free of thermal stratification.

Second; to provide a control system for furnaces which will increase theoperating time of each cycle of operations over that of the usualoperating cycle.

Third; to provide a control system which will materially reduce thedifferential in room temperatures between warm and cold stages.

Fourth; to provide a 'control system which will automatically regulatethe duct temperatures in accordance with the demand for heat.

Fifth; to provide a system which will automatically regulate ,theregister outlet temperatures in conformity with heat demands.

Sixth; to provide an automatic control which will maintain the outlettemperatures below a predetermined value irrespective of variations inthe volume of air flowing through the furnace.

Seventh; to provide a heating system which will cause delivery of airwhich is heated to varying temperatures proportionate to the demanddelivery and delivering no heat when a defined room temperature exists,and delivering low heat for low temperature differentials and high heatwith higher temperature differentials as related to a maximum. normaltemperature.

Eighth; toprovide a system in which the fuel supply to the furnace iscontrolled to initiate heating at full capacity and to reduce thecapacity as heating progresses and proportionate to the demand for heat.

In decribing theinvention reference will be made to the accompanyingdrawing, which is a diagrammatic view of a warm-air furnace with anassociated wiring diagram illustrating the 'rneeonvencemi warm airfurnace includes a furnace casing l having a duct H which has branchesconnecting to various registers in the rooms to be heated, and whichbranches and registers are well known and require therefore neitherdescription nor illustration. In addition, a burner l2 has a fuelconnection l3 which is provided with a suitable fuel control,

In this invention the controls can be readily formed into a single unit,but which are here illustrated as consisting of separate controls. Twoof these controls; l4 and Hi, are preferably of the time-delay-openingtype described in my Patent Number 2,118,443, granted May 24, 1938, forElectric valve; and the third control consists of a bypass l6 controlledby a suitable valve H which controls the amount of fluid delivered tothe control l4, and is therefore an associated element thereof. Thisbypass can be arranged according to known means in which the valve inthe control I5 is prevented from fully closing and thereby functioningas the bypass, displacing|6 and-H. I

Both controls l4 and I! are adapted to pass a full supply -of fuel inseries from the fuel supply line EB'tothe fuel connection l3, but thecontrol M is limited to the amount passing through the adjusted valve"IT or its equivalent in the" control Hi When the control i5 is closed,therefore the amount of fuel reaching'the burner is dependent uponwhether both controls are open, whether control I5 is closed, andwhether control I4 is closed, and creatingrespectively high, low, and nofire.

These controls are of the conventional type suited to the particulartype of fuel used, and in which'an electrically-heated thermostat or anelectromagnet controls the opening and closing of a valve forcontrolling admission and passage of fuel to the burner H, thestructures being well known in the art and therefore not illustrated indetail.

The conventional forced draft type warm air furnace also includes ablower or-fan l9 driven by a motor for forcing the heated air throughthe furnace casing to the registers previously mentioned. The motor 20is controlled by a thermostatic control switch or relay 2| which iscontrolled by the heat within the casing and starts operation of themotor and its associated fan as soon as the temperature within thecasing rises ,to a, predetermined value, and discontinues operation whenthe temperature drops back to a point below said predetermined value,and this motor and control are connected to the main source of potential22, 23 through wires 24, 25 and 26.

' A suitable thermostatic control 21 is associated with the furnacecasing and controlled by the heat therein, and is preferably of a typesimilar -to that illustrated and described in my copending applicationSerial Number 241,808, filed November 22, 1938, now Patent Number2,227,732, dated January 7, 1941, for Thermally-controlled switch, and asecond control of similar or suitable type is associated with either themain duct or'with a branch thereof, and is indicated at 28 as associatedwith the main duct, and it is 'controlled by the heat within the ductwith which it is associated. A third control 29 which is of the doubleor two-step control of room thermostat, has two bimetal elements 30 and3| which respectively form circuit control devices in combination withthe respective contacts 32 and 33. These elements have a commonconnection 34 to one side 35 of the secondary of a low voltagetransformer 36, and the two contacts 32 and 33 are respectivelyconnected through the respective wires 31 and 38 to one side each of therespective fuel flow controls l5 and I4.

The other side of each of the two controls I5 and H are respectivelyconnected through wires 39 and "to one side of the control 21 the otherside of which is connected through a wire 4| to the other side of thesecondary of the transformer 36 the primary of which is connected to thesource of potential 22, 23.

The control 28 has one side connectedthrough a wire 42 to contact 33 andthe other side is connected through a wire 43 to the one side 4d of thecontrol I5. A switch 45 is provided for manual control of all of thecircuits.

The operation of the system is as follows: The element 30 and itscontact 33 forms the high temperature side of the room thermostat and isadjusted to break contact at a predetermined room temperature, usuallyF., while the element 3| with its contact 32 forms the minimumtemperature side and breaks contact at a slightly lower temperature,about 69". Switch 45 is closed the room temperature drops to 69 or tothat for which the element 3| is adjusted and the circuit is therebyclosed from the secondary of the transformer 36 through wire 34- andswitch 45, element 3|, contact 32, wirefil to one side 44 of thehigh-flow control 85, and thence from the other side 46, wire 39, wire40 to control 21, and thence through wire 4| to the other side of thesecondary of the transformer, control 21 being closed, since the furnaceis cold.

A second circuit is completed from the secondary of the transformerthrough wire 34, switch 45, element 30, contact 33, wire 38 to one side4'! of fuel control 4, thence from the other side 48 through wire 40 tothe control 21 to wire 4|.

A third circuit is completed through wire 42 to control 28, thencethrough wire 43 to the one side 44 of the fuel control l5 and thencethrough wires 39 and 40 to the secondary of the trans.- former.

Closing. of all circuits opens both fuel controls l4 and I5 and admitsfuel through connection i3 to the burner |2 at full capacity, andheating of the furnace is started.

As soonas heatinghas progressed to a predetermined degree, the control2| closes a circuit from power line 23 through wire 25, control 2|, Wire24, motor 20, wire 26 to the other power line 22, starting the fan,which forces the heated air within the furnace casing out through theduct andwhen the heat within the furnace casing reaches a predeterminedvalue, the circuit is broken to both fuel controls closing off theburner l2, the fan continuing to oper-. ate, and thus the temperaturewithin the casing is controlled.

aaoaoea predetermined minimum temperature, element combination,controlfl functioning only to completely shut off the fuel supply in theevent of excessive casing heat.

As the room temperature rises to the maximum point, contact is broken at30, 33, breaking allof the circuits with the exception of the fancircuit, and closing both fuel controls It and [5, and after the heatwithin the casing drops to a predetermined value the circuit to the fanmotor is broken and circulation ceases, except as to thermal influenceof the heat within the casing and ducts.

The condition. described would rarely be attained, since with thissystem, as soon as the slightest drop occurred in temperature below themaximum, the circuit will be recompleted through .element 30 and contact33 to the-control ll, further controlled by the control 28 in the duct,thus uniform room temperature is maintained.

If sufllcient heat is not provided by this arrangement, to maintain theroom temperature above the minimum, the first circuit will be againcompleted through element 3| and contact 32 to the high fire side of thefuel delivery control.

Thus there are three circuits in parallel, each dependent upon theother, each cooperating with the other, and each being selective inconformity with temperature conditions and the demand for heat.

Thus the fan is operatedcontinuously over considerable periods of timedue to the extreme flexibility of'the control and precisionmaintenanceof temperatures, thus preventing thermal stratification in the room dueto more constant fan operation.

It will be understood that variations in the method and in theconstruction and arrangement of parts, which variations are consistentwith the appended claims may be resorted to without detracting from thespirit or scope of the invention, or sacrificing any of the advantagesthereof.

I claim: I

1. A heating system comprising a furnace having a casing and a duct; afuel supply line; a fan and driving means and control means for saiddriving means and controlled by the heat within the casing; a first fuelcontrol and a second fuel control connected in series in said fuel lineand a by-pass about said first fuel control and means for manuallyadjusting the passage for fuel through said by-pass for delivering apredetermined restricted amount of fuel through said second fuelcontrol; thermostatic control means controlled by the heat in saidcasing and controlling said first and second fuel controls forterminating delivery of fuel under excess heat conditions in saidcasing; thermostatic control means controlled by the heat in said ductand controlling said first fuel control for terminatfor controlledrespectively by established maximum and minimum room temperatures andcontrolling both of said fuel controls for maximum delivery of fuelthrough both controls under room temperatures below said minimum vandfor restricted delivery when the room temperature exists between saidmaximum and minimum when the heat in said duct is at a predeterminedmaxi mum and for termination of fuel delivery when room temperaturesattain said maximum temperature.

2. A heating system comprising a furnace having a casing, a duct; 9,fuel line and a fuel control means in said fuel line for selectivelygauging delivery of fuel in varying amounts and for termination ofdelivery: first control means associated with said casing and controlledby the heat therein and controlling said fuel control means to terminatedelivery of fuel in the event of existent abnormal heat conditions insaid casing; second control means associated with said duct controllingsaid fuel control for delivery of fuel in restricted amount in the eventof abnormal heat conditions in said duct and for delivery in maximumamountunder subnormal heat conditions in said duct; and third controlmeans controlled by existent room temperatures and elec tricallyassociated with said fuel control and with saidfirst andsecond controlsand controlling delivery of fuel selectively for maximum delivery offuel below a predetermined minimum room temperature, alternaterestricted and maximum delivery under control of said second controlunder temperatures between said predetermined minimum and apredetermined maximum, and

termination of delivery when said room temperaing delivery of fuelthrough said first control for delivery of fuel only through said secondcontrol in restricted amount under excess temperature conditions in saidduct; and a room therfecting a substantially uniform continuous roomtemperature within the limits of minimum and maximum temperatures.

3. A heating system comprising a furnace having a casing, a duct, afuelline; a first thermostatic switch operable to open under the infiu--ence of heatin said casing; a second thermostatic switch operable underthe influence of heat within said duct; a room thermostat including afirst switch and a second switch both of which are closed when the roomtemperature is below an established minimum and sequentially opened inresponse to successive rises in room tempera minationof delivery, andthree circuits in parallel including respectively; said first switch,said fuel control for low delivery of fuel and said first thermostaticswitch; said first switch, said second thermostatic switch, said fuelcontrol for high fuel delivery, and said second thermostatic switch;and, said second switch, said fuel control for high delivery of fuel,and said first thermostatic switch, whereby when the existent roomtemperature is below the established minimum, high fuel delivery isprovided without control by the duct temperature, and when the existentroom temperature is between the established minimum and maximum, highand low fuel delivery are alternated through control by the ducttemperature for maintaining a substantially constant duct temperature,and when the existent room temperature is at or above its establishedconsisting in maintaining a cold furnace when mostat having Contacts andcircuits h 78 there is no demand for heat by a space, operatin thefurnace when the space temperature drops below a predetermined maximum,under control of the duct temperature, with high fire when the ducttemperature is below'a predetermined value, and low fire when the ducttemperature reaches said predetermined value, to maintain asubstantially constant temperature in the duct while the spacetemperature is between said predetermined maximum and a predeterminedminimum; operating the furnace under high fire without influence by theduct temperature when the space temperature drops below saidpredetermined minimum; reverting to alternate high and low fire undercontrol of the duct temperature as previously recited when the spacetemperature rises above said predetermined minimum, and discontinuingall fire other than the pilot when either the space temperature reachessaid predetermined maximum, or when the casing temperature attains apredetermined maximum.

5. A furnace control comprising; a room thermostat, a duct thermostat,and a casing thermostat; a fuel line and selective control means forhigh and low delivery of fuel therefrom and for termination of deliveryof fuel; a source of potential; a first circuit including said source ofpotential, said room thermostat, said selective control means for lowdelivery of fuel, and said casing thermostat; and a second circuitincluding said source of potential, said room thermostat, said ductthermostat, said selective control means for high delivery of fuel, andsaid casing thermostat; said thermostats respectively breaking circuitsat established difierent temperatures; said room thermostat completingthe circuits when the room temperature drops below an ing said secondcircuit to interrupt high delivery breaking all circuits when said roomtemperature reaches its established maximum.

6. A structure as defined in claim 5; said room thermostat having twocircuit control means operable sequentially with successive increases ordecreases in temperature, said first and second circuits beingcontrolled by one of said circuit control means; and a third circuitincluding the other of said circuit control means, said fuel control forhigh delivery of fuel, said casing thermostat, and said source ofpotential; whereby high delivery of fuel is established and maintainedby said third circuit uninfiuenced by said duct thermostat or by theother circuits when said third circuit is completed through a recessionin the room temperature below an established minimum and beinginterrupted to transfer control to the other circuits and the ductthermostat when said minimum is attained through a rise in roomtemperature.

7. A furnace control comprising; a source of potential and first,second, and third circuits; a space thermostat having first and secondcircuitcontrol means connected in parallel to said source of potential;said first circuit-control means operating to close said first andsecond circuits when the temperature of the space drops below anestablished maximum; said second circuit-control means operating toclose said third circuit when the temperature of the space drops belowan established minimum: a duct thermostat included in, and operating toopen said first

